The U.S.S. Enterprise, obeying orders from the highest ranks of Starfleet Command, beams aboard a special emissary named K'Ehleyr, a half-human, half-Klingon female. The crew is pulled by Worf's coldness toward K'Ehleyr, who informs them that they must intercept the T'Ong, a Klingon vessel whose staff has been in cryogenic sleep for a century. She reveals that the Klingons began their voyage while the Federation was still at war with the Klingon Empire, and that if they awaken within striking range of key Federation outposts, the results could be devastating.
Worf, shunning the emissary's friendly advances, reluctantly follows Picard's orders to meet with K'Ehleyr about the volatile situation with the T'Ong. However, their meeting quickly turns personal, revealing that the two were once linked romantically. After a bitter argument, K'Ehleyr storms out.
To work out her frustrations, K'Ehleyr goes to the Holodeck where she does Worf's rigorous calisthenics program. Worf joins her for the exercise, which pits them in battle against deadly alien warriors. After completing the program, an aroused Worf grabs K'Ehleyr and they consummate their passion. At dawn, Worf asks her to take the Klingon oath of marriage which traditionally follows intimacy, but she refuses.
Meanwhile, the Enterprise approaches the T'Ong, whose newly awakened crew members begin firing at the ship. To prevent a fatal face-off, Worf dresses in full Klingon Captain's regalia and presents himself to the T'Ong as the commander of the U.S.S. Enterprise and demands their surrender. He convinces the Klingon leaders that the war ended during the T'Ong's mission and that the Klingons are now peaceful members of the Federation.
Following the T'Ong's surrender, K'Ehleyr prepares to take command of the Klingon vessel and is escorted to the transporter room by Worf. There, the two finally reconcile their differences and although K'Ehleyr bids him farewell, she leaves Worf with the hope that their paths will cross again.